Yarn with improved hydrolytic stability from aromatic polyamide comprising chloroterephthalamide units

ABSTRACT

Aromatic polyamide fibers of high hydrolytic stability are disclosed. The polyamide is a copolymer including chloroterephthalamide or a blend of homopolymers including one with chloroterephthalamide; and the fibers are dried under tension or heat treated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to para-aramid fibers with excellent physicalproperties and a high degree of hydrolytic stability; and to a processfor making such fibers.

2. Description of the Prior Art

U.S. Pat. No. 3,560,137, issued Feb. 2, 1971 on the application of Hahn,discloses aromatic polyamides having increased hydrolytic durability.Hahn recognized the need for increased hydrolytic stability in fiberswhich had been damaged by crimping and disclosed that poly(metaphenyleneisophthalamide) fibers should be subjected to a heat treatment after thecrimping, under no tension.

U.S. Pat. Nos. 3,869,429 and 3,767,756, issued Mar. 4, 1975 and Oct. 23,1973, respectively, on the applications of Blades, disclose highstrength para-aramid fibers. The Blades patents disclose a variety ofcopolymer compositions for the para-aramid fibers; and specificallydisclose a homopolymer using chloroterephthaloyl chloride and copolymersusing chloroterephthaloyl chloride and terephthaloyl chloride in moleratios of 5/95 and 50/50. There is disclosure of drying at 150°-160° C.and it is recommended that low tension be used. As to heat treating,general disclosed conditions are 150°-550° C. for durations of 1-6seconds at tensions of 0.5-12 gpd.

U.S. Pat. No. 3,869,430, issued Mar. 4, 1975 on the application ofBlades, discloses heat treatment for para-aramid fibers wherein thefibers are subjected to temperatures of, preferably, 250°-600° C. for0.5-5 seconds and 1-8 gpd. This patent contains no reference tochloro-containing para-aramid copolymers.

U.S. Pat. No. 3,671,542, issued June 20, 1972 on the application ofKwolek, discloses fibers made from homopolymer of poly(p-phenylene2,5-dichloroterephthalamide) and heat treating those fibers.

SUMMARY OF THE INVENTION

The present invention provides yarns of greatly improved hydrolyticstability made from fibers of aromatic polyamides with at least 10 molepercent chloroterephthalamide in the polymer composition. The polymercomposition includes copoly(p-phenyleneterephthalamide/chloroterephthalamide) (hereinafter "PPD-T/ClT") usedalone; and also includes blends of such copolymer with poly(p-phenyleneterephthalamide) homopolymer. The yarns of PPD-T/ClT copolymer andblends of copolymer with homopolymer, when heat treated or dried undertension according to the invention, exhibit tensile propertiescomparable with fibers made from PPD-T homopolymer--tenacity of greaterthan 18 grams per denier; but having dramatically improved hydrolyticstability.

DETAILED DESCRIPTION OF THE INVENTION

Fibers of aromatic polyamides are well known for their high strength andhigh modulus. There has long been a need, however, for fibers of suchhigh strength and high modulus which, also, have high stability onexposure to aqueous, particularly alkaline, environments. Fibersexhibiting a high hydrolytic stability will find particular use in suchfields as reinforced piping and underwater roping, as well as, otherapplications involving water contact.

The fibers of this invention can be made exclusively from copolymershaving chloroterephthalamide or they can be made from blends of suchcopolymers or homopolymers with chloroterephthalamide and PPD-Thomopolymer. It is an important element of the description of thisinvention to note that the hydrolytic stability of these fibers exhibitsa remarkable and surprising jump at greater than 10 mole percentchloroterephthalamide content and most notably at 20 mole percent andgreater. Making the Copolymer.

PPD-T/ClT copolymers used in the fibers of the present invention aremade up of p-phenylene diamine as the diamine and terephthaloyl chlorideand chloroterephthaloyl chloride, in the form of monochloroterephthaloylchloride and dichloroterephthaloyl chloride, as the acid chloride. Thechloroterephthaloyl chloride is, generally, greater than 70 mole percentmonochloroterephthaloyl chloride and less than 30 mole percentdichloroterephthaloyl chloride; and such is preferred for practice ofthis invention. Substantially pure monochloroterephthaloyl chloride anddichloroterephthaloyl chloride, although rather difficult to obtain,can, also, be used in practice of this invention. It is to be understoodthat up to as much as 5 mole percent of the diamine can be other thanp-phenylene diamine and that up to as much as 5 mole percent of the acidchloride can be other than the terephthaloyl chloride andchloroterephthaloyl chloride. The limit of 5 mole percent is ratherarbitrary because substitute monomers which are very similar to theinitial monomers can be used in greater amounts and, in some cases wherethe substitute monomers are greatly different from the initial monomers,less than 5 mole percent can be used. The amount of substitute monomerswhich can be tolerated in the practice of this invention, depends uponwhether or not the substitute monomers so alter the character of thecopolymer that fibers made from that copolymer are not within theinvention.

The polymer composition used in practice of this invention can includeusually-used additives such as dyes, fillers, delusterants, stabilizers,anti-oxidants and the like.

The copolymer and the PPD-T homopolymer, when used, can be convenientlymade by any of the well known polymerization processes such as thosetaught in U.S. Pat. Nos. 3,063,966 and 3,869,429. One process for makingthe copolymer of this invention includes dissolving one mole ofp-phenylene diamine in a solvent system comprising about one mole ofcalcium chloride and about 2.5 liters of N-methyl-2-pyrrolidone and thenadding a blend of one mole, total, of the terephthaloyl chloride andchloroterephthaloyl chloride with agitation and cooling. The addition ofthe diacid chlorides is usually accomplished in two steps--the firstaddition step being about 25-35 weight percent of the total with thesecond addition step occurring after the system has been mixed for about15 minutes. Cooling is applied to the system after the second additionstep to maintain the temperature below about 75° C. Under forces ofcontinued agitation, the copolymer gels and then crumbles; and, after atleast thirty minutes, the resulting crumb-like copolymer is allowed tostand without agitation for several hours and is then washed severaltimes in water and dried in an oven at about 100°-150° C. Othercopolymers of this invention can be made in accordance with the processoutlined above when the mole fraction of chloroterephthaloyl chloride isfrom 0.05 to 1.0 based on total acid chlorides. When the copolymerincludes more than about 85 mole percent chloroterephthalate, thecopolymer does not gel and no crumb is formed--the reaction systemsimply becomes very viscous as the polymerization proceeds toconclusion.

Molecular weight of the polymer is dependent upon a multitude ofconditions. For example, to obtain polymer of high molecular weight,reactants and solvent should be free from impurities and the watercontent of the total reaction system should be as low as possible--atleast less than 0.03 weight percent. Care should be exercised to usesubstantially equal moles of the diamine and the diacid chlorides inorder to assure highest molecular weight.

The polymers of this invention can also be made by continuouspolymerization and other solvents can be used such as tetramethyl urea,dimethyl acetamide, hexamethyl phosphoramide, and the like, alone or incombination with N-methyl-2-pyrrolidone. While it may be preferred thatinorganic salts be added to the solvent to assist in maintaining asolution of the copolymers as it is formed, quaternary ammonium saltshave, also, been found to be effective in maintaining the copolymersolution. Examples of useful quaternary ammonium salts include: methyltri-n-butyl ammonium chloride; methyl tri-n-propyl ammonium chloride;tetra-n-butyl ammonium chloride; and tetra-n-propyl ammonium chloride.

Yarns of this invention are made by extruding a dope of the copolymer orpolymer blend by the dry-jet wet spinning processes, such as are taught,for example, in U.S. Pat. No. 3,767,756.

A dope can be prepared by dissolving an adequate amount of the polymerin an appropriate solvent. Sulfuric acid, chlorosulfuric acid,fluorosulfuric acid and mixtures of these acids can be identified asappropriate solvents. Sulfuric acid is much the preferred solvent andshould, generally, be used at a concentration of 98% by weight orgreater. It has been determined, however, that increasing mole fractionsof chloroterephthalamide will permit use of less concentrated sulfuricacid. The polymer should be dissolved in the acid in the amount of atleast 40, preferably more than 43 grams of polymer per 100 millilitersof solvent. The densities, at 25° C., of the acid solvents are asfollows: 98% H₂ SO₄, 1.83 g/ml; HSO₃ Cl, 1.79 g/ml; and HSO₃ F, 1.74g/ml.

Before preparation of the spinning dope, the copolymer and homopolymer,if used, and other ingredients should be carefully dried, preferably toless than one weight percent water; the polymer and the solvent shouldbe combined under dry conditions; and the dope should be stored underdry conditions. Care should be exercised to exclude atmosphericmoisture. Dopes should be mixed and held in the spinning process at aslow a temperature as is practical to keep them liquid in order to reducedegradation of the polymer. Exposure of the dopes to temperatures ofgreater than 90° C. should be minimized.

The dope, once prepared, can be used immediately or stored for futureuse. If stored, the dope is preferably frozen and stored in solid formin an inert atmosphere such as under a dry nitrogen blanket. If the dopeis to be used immediately, it can conveniently be made continuously andfed directly to spinnerets. Continuous preparation and immediate useminimizes degradation of the polymer in the spinning process.

The dopes are, typically, solid at room temperature. The bulk viscosityof dopes made with a particular polymer increases with molecular weightof the polymer for given temperatures and concentrations and the bulkviscosity of dopes decreases with increasing mole fractions ofchloroterephthalamide.

Dopes can generally be extruded at any temperature where they aresufficiently fluid. Since the degree of degradation is dependent upontime and temperature, it is important that temperatures be as low aspossible. Temperatures below about 90° C. are preferable andtemperatures of about 75° to 85° C. are usually used. If highertemperatures are required or desired for any reason, processingequipment should be designed so that the dope is exposed to the highertemperatures for a minimum time.

Dopes used to make the yarns of this invention are opticallyanisotropic, that is microscopic regions of a dope are birefringent anda bulk sample of the dope depolarizes plane-polarized light because thelight transmission properties of the microscopic regions of the dopevary with direction. It is believed to be important that the dopes usedin this invention must be anisotropic, at least in part.

Dopes are extruded through spinnerets with orifices ranging from about0.025 to 0.25 mm in diameter, or perhaps slightly larger or smaller. Thenumber, size, shape, and configuration of the orifices are not critical.The extruded dope is conducted into a coagulation bath through anoncoagulating fluid layer. While in the fluid layer, the extruded dopeis stretched from as little as 1 to as much as 15 time its initiallength (spin stretch factor). The fluid layer is generally air but canbe any other inert gas or even liquid which is a noncoagulant for thedope. The noncoagulating fluid is generally from 0.1 to 10 centimetersin thickness.

The coagulation bath is aqueous and ranges from pure water, or brine, toas much as 70% sulfuric acid. Bath temperatures can range from belowfreezing to about 28° C. or, perhaps, slightly higher. It is preferredthat the temperature of the coagulation bath be kept below about 10° C.,and more preferably, below 5° C., to obtain fibers with the highestinitial strength.

As the extruded dope is conducted through the coagulation bath, the dopeis coagulated into a water-swollen fiber and is ready for drying and, ifdesired, heat treatment. The fiber includes about 20 to 100% percentaqueous coagulation medium, based on dry fiber material, and, for thepurposes of this invention, must be thoroughly washed to remove the saltand acid from the interior of the swollen fiber. Fiber-washing solutionscan be pure water or they can be slightly alkaline. The washing can becontrolled by immersing spools of the fiber in a washing bath or bypassing the fiber through a bath or spray of washing liquid. Care shouldbe exercised to remove as much as possible of the salt and acid residuefrom the spinning process.

The heat treatment and high tension drying of this invention areconducted on never-dried fibers; and, for purposes of this invention,"never-dried" means that the fibers have been newly-spun and never driedto less than 20 percent moisture prior to operation of the heat treatingor drying under tension. Never-dried fibers may have from 20 to 100percent moisture, based on the weight of the polymer. It is believedthat previously-dried fibers cannot successfully be heat treated ordried under tension for this invention because the heat treatment anddrying under tension is effective only when performed on the polymermolecules at the time that the structure is being dried and ordered intoa compact fiber and before the structure has been collapsed by removalof the water.

High tension drying is conducted by subjecting never-dried fibers to atension of 1-12 grams per denier at a temperature of 100° to 250° C.,preferably 160°-80° C., for a time of 15-25 seconds. The preferredtension is 2-6 grams per denier and the temperature and time should beselected within the above-noted ranges to achieve a final moisture onthe yarn of about 8-14%. The high tension drying is convenientlyconducted by wrapping the never-dried yarn several times over a steamheated roll with the number of wraps selected to achieve the desireddrying time.

Heat treating is conducted by exposing never-dried fibers in an oven totemperatures of 250°-500° C. for 1.5-12 seconds under a tension of 1-12grams per denier. The preferred conditions are 350°-400° C. for 2-8seconds at 2-6 grams per denier.

TEST PROCEDURES

Inherent Viscosity. Inherent Viscosity (IV) is defined by the equation:

    IV=1n(η.sub.rel)/c

where c is the concentration (0.5 gram of polymer in 100 ml of solvent)of the polymer solution and η_(rel) (relative viscosity) is the ratiobetween the flow times of the polymer solution and the solvent asmeasured at 30° C. in a capillary viscometer. The inherent viscosityvalues reported and specified herein are determined using concentratedsulfuric acid (96% H₂ SO₄).

Tensile Properties. Yarns tested for tensile properties are, first,conditioned and, then, twisted to a twist multiplier of 1.1. The twistmultiplier (TM) of a yarn is defined as:

    TM=(twists/inch)/(5315/denier of yarn).sup.-1/2

The yarns to be tested are conditioned at 25° C., 55% relative humidityfor a minimum of 14 hours and the tensile tests are conducted at thoseconditions. Tenacity (breaking tenacity), elongation (breakingelongation), and modulus are determined by breaking test yarns on anInstron tester (Instron Engineering Corp., Canton, Mass.).

Tenacity, elongation, and initial modulus, as defined in ASTMD2101-1985, are determined using yarn gage lengths of 25.4 cm and anelongation rate of 50% strain/minute. The modulus is calculated from theslope of the stress-strain curve at 1% strain and is equal to the stressin grams at 1% strain (absolute) times 100, divided by the test yarndenier.

Denier. The denier of a yarn is determined by weighing a known length ofthe yarn. Denier is defined as the weight, in grams, of 9000 meters ofthe yarn.

In actual practice, the measured denier of a yarn sample, testconditions and sample identification are fed into a computer before thestart of a test; the computer records the load-elongation curve of theyarn as it is broken and then calculates the properties.

Hydrolytic Stability. Hydrolytic Stability is reported as percent ofbreak strength (tenacity) retained after a certain exposure to anaqueous alkaline environment. To perform the test, a portion of a lengthof finished yarn is immersed in an aqueous 10% solution of sodiumhydroxide at 95° C. for 20 hours; and the yarn is, then, thoroughlywashed and dried at ambient temperatures under no tension. Tenacitydeterminations are conducted on the treated yarn (T¹) and, as a control,on the untreated yarn (T²). The hydrolytic stability is: ##EQU1##

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the examples provided, below, all amounts are in mole percent or moleratio, unless specified otherwise.

EXAMPLE A Preparation of 2-chloroterephthaloyl chloride (ClTCl) and2,5-dichloroterephthaloyl chloride (DClTCl)

This example illustrates the preparation of 2-chloroterephthaloylchloride (ClTCl) and 2,5-dichloroterephthaloyl chloride (DClTCl) by thechlorination of terephthaloyl chloride and subsequent separation using4-stage distillation.

High-purity terephthaloyl chloride (TCl) was chlorinated with chlorinegas in a reaction vessel in the presence of ferric chloride at 150° C.for 24 hours. The resulting chlorination products were approximately 50%TCl, 37% ClTCl and 13% DClTCl. The chlorination products were distilledin a 60-tray distillation column and separated into two fractions:approximately 60 wt. % heavy fraction containing 25/56/18TCl/ClTCl/DClTCl, and approximately 40 wt. % light fraction containing78/9/13 TCl/ClTCl/DClTCl. The ClTCl-rich fraction was distilled andseparated into a heavy fraction containing mostly ClTCl and DClTCl andtrace amount of TCl, and a light fraction containing mostly TCl andabout 1% ClTCl. The heavy fraction from the second-stage distillationwas flash distilled to remove small amounts of tar materials. The flashdistillate was redistilled and separated into a heavy fractioncontaining 99.7/0.3 ClTCl/DClTCl and a light fraction containing3/97/<0.3 TCl/ClTCl/DClTCl.

EXAMPLE B Preparation of 95/5 PPD-T/ClT Copolymer

This example illustrates the preparation of a 95/5 copoly(p-phenyleneterephthalamide/2-chloroterephthalamide (PPD-T/ClT) by low temperaturepolycondensation in a large stirred reactor.

In a stirred reactor under nitrogen atmosphere, 11.4 gallons anhydrousN-methylpyrrolidone (NMP), 2761 g (25.53 moles) p-phenylenediamine(PPD), and 3854 g (34.72 moles) anhydrous calcium chloride were stirredwith the main stirrer at room temperature for 3 hours until all salt anddiamine were dissolved. The mixture was cooled to 5° C., and 1816 g(8.95 moles) terephthaloyl chloride (TCl) were rapidly added. Themixture was stirred for ten minutes at ambient temperature and recooledto 5° C. A diacid chloride mixture containing 3140 g (15.47 moles)terephthaloyl chloride and 287 g (1.21 moles) 2-chloroterephthaloylchloride (ClTCl), was rapidly added. The resulting mixture was stirredunder nitrogen at ambient temperature. A secondary stirrer/chopper wasactivated 3 to 8 minutes after the second-stage addition of acidchloride to reduce the polymer particle size. The mixture temperaturewas controlled at less than 70° C., preferably 65° C. The polymerizationmixture was stirred with the main stirrer and the chopper for 200-300additional minutes, and left standing overnight at room temperatureunder nitrogen in the reaction vessel without stirring. The polymermixture was then discharged from the reactor. (In some cases as will beshown in the following examples, it was necessary to break up thepolymer mixture after standing by further stirring with the reactorstirrer and the chopper under nitrogen at ambient temperature beforedischarging it.) The polymer mixture was washed and filtered with 35gallons of deionized water 25 times to isolate the polymer. The isolatedpolymer was neutralized to pH>6, and dried at 120° C. under vacuum. Theinherent viscosity of the dry polymer was 7.7 dl/g.

EXAMPLE C Preparation of 90/10 PPD-T/ClT Copolymer

This example illustrates the preparation of a 90/10 copoly(p-phenyleneterephthalamide/2-chloroterephthalamide). The procedure of Example B wasrepeated except that the acid chloride for the second-stage additioncontained 2896 g (14.26 moles) terephthaloyl chloride and 567 g (2.39moles) 2-chloroterephthaloyl chloride, and that the polymer mixture wasstirred with the stirrer and the chopper for 180 minutes, left standingovernight under nitrogen, and mixed 120 additional minutes before it wasdischarged from the reactor. The polymer thus obtained had an inherentviscosity of 7.63 dl/g.

EXAMPLE D Preparation of 80/20 PPD-T/ClT Copolymer

This example illustrates the preparation of an 80/20 copoly(p-phenyleneterephthalamide/2-chloroterephthalamide). The procedure of Example B wasrepeated except that the acid chloride for the second-stage additioncontained 2415 g (11.90 moles) terephthaloyl chloride and 1135 g (4.80moles) 2-chloroterephthaloyl chloride, and that the polymer was mixedwith the stirrer and chopper for 195 minutes. The maximum reactiontemperature was 61° C. The polymer mixture was left standing overnightunder nitrogen, and mixed for 60 additional minutes before it wasdischarged from the reactor. The polymer thus obtained had an inherentviscosity of 5.88 dl/g.

EXAMPLE E Preparation of 70/30 PPD-T/ClT Copolymer

This example illustrates the preparation of a 70/30 copoly(p-phenyleneterephthalamide/2-chloroterephthalamide). The procedure of Example B wasrepeated except that the acid chloride for the second-stage additioncontained 1859 g (9.16 moles) terephthaloyl chloride and 1779 g (7.49moles) 2-chloroterephthaloyl chloride, and that the polymer mixture wasmixed with the stirrer and chopper for 230 minutes, left standingovernight under nitrogen, and mixed for 90 additional minutes before itwas discharged from the reactor. The polymer thus obtained had aninherent viscosity of 5.9 dl/g.

EXAMPLE F Preparation of 60/40 PPD-T/ClT Copolymer

This example illustrates the preparation of a 60/40 copoly(p-phenyleneterephthalamide/2-chloroterephthalamide). The procedure of Example B wasrepeated except that the acid chloride for the second-stage additioncontained 1354 g (6.67 moles) terephthaloyl chloride and 2372 g (9.99moles) 2-chloroterephthaloyl chloride, and that the polymer mixture wasmixed with the stirrer and chopper 114 minutes and was discharged fromthe reactor without overnight standing or additional mixing. The polymerthus obtained had an inherent viscosity of 5.4 dl/g.

EXAMPLES G, H, I Preparation of 50/50, 40/60, and 30/70 PPD-T/ClTCopolymers

For preparation of these copolymers, the procedure of Example B wasrepeated except that the acid chloride was added in three stages;--theadditions each including 30, 35, and 35 weight percent of the total acidchlorides. In the table below, are designated the total amounts of TCland ClTCl, as well as the weight percent of the TCl in the additions ofeach stage and the inherent viscosity of each copolymer.

    ______________________________________                                        TCl (%/stage)                                                                 TCl (g)   1st    2nd     3rd   ClTCl (g)                                                                              IV (dl/g)                             ______________________________________                                        G   2569      60     20    20    2772     4.7                                 H   2021      76     12    12    3404     5.2                                 I   1409      87     6.5   6.5   3833     3.9                                 ______________________________________                                    

EXAMPLE J Preparation of Poly(p-phenylene chloroterephthalamide)(PPD-ClT)

This example illustrates the preparation of poly(p-phenylenechloroterephthalamide). The procedure of Example B was repeated exceptthat 1260 g (11.65 moles) PPD and 2014 g (18.14 moles) anhydrous calciumchloride were stirred with the main stirrer at room temperature forthree hours until all salt/diamine were dissolved and that the acidchloride for the first stage addition was 950 g (4.01 moles) ClTCl andthe second stage was 1812 g (7.65 moles) ClTCl. The solution becameviscous within 5 minutes, but the polymer did not gel or precipitate.The polymerization mixture was stirred with the main stirrer only for150 minutes under nitrogen and ambient temperatures. Water was added insmall portions to the reaction mixture in a blender to precipitate thepolymer. The precipitated fibrous polymer was then washed and filteredwith 35 gallons of deionized water 25 times to isolate the polymer. Theisolated polymer was neutralized to pH>6 and dried at 120° C. undervacuum. The inherent viscosity of the polymer thus obtained was 4.2dl/g.

EXAMPLE K Preparation of 95/5 PPD-T/DClT Copolymer

This example illustrates the preparation of a 95/5 copoly(p-phenyleneterephthalamide/dichloroterephthalamide) (PPD-T/DClT) by low temperaturepolycondensation in a large stirred reactor.

To prepare the dichloro copolymer of this Example, the procedure ofExample B was followed exactly using the same kinds and amounts ofmaterials except that 3116 g (15.34 moles) TCl and 357 g (1.308 moles)dichloroterephthaloyl chloride (DClTCl) were added in the secondaddition step. The inherent viscosity of the dried polymer was 6.2 dl/g.

EXAMPLE L Preparation of 90/10 PPD-T/DClT Copolymer

This example illustrates the preparation of a 90/10 copoly(p-phenyleneterephthalamide/dichloroterephthalamide) (PPD-T/DClT) by low temperaturepolycondensation in a large stirred reactor. The procedure of Example Kwas repeated except that the acid chloride for the second stage additioncontained 2851 g (14.04 moles) TCl and 714 g (2.63 moles) DClTCl. Theacid chloride mixture was stirred 200 minutes, stored overnight undernitrogen, and discharged into the reactor. The inherent viscosity ofpolymer thus obtained was 5.6 dl/g.

EXAMPLE M Preparation of 82/18 PPD-T/DClT Copolymer

This example illustrates the preparation of a 82/18 PPD-T/DClTcopoly(p-phenyleneterephthalamide/dichloroterephthalamide) by lowtemperature polycondensation in a large stirred reactor. The procedureof Example K was repeated except that the acid chloride for the secondstage addition contained 2428 g (11.96 moles) TCl and 1282 g (4.72moles) DClTCl. The acid chloride mixture was stirred 235 minutes, storedovernight under nitrogen, and discharged into the reactor. The inherentviscosity of the polymer was 4.8 dl/g.

EXAMPLE N Preparation of 79.5/16/4.5 PPD-T/ClT/DClT Copolymer

This example illustrates the feasibility of preparing a PPD-T/ClT/DClTcopolymer from a mixture of acid chlorides which is obtainable from thefirst-stage distillation of the chlorination products. The procedure ofExample B was repeated except that a synthetic mixture of acid chlorideswas prepared by mixing TCl, ClTCl and DClTCl in the mole ratio of79.5/16/4.5. The polymer thus obtained had an inherent viscosity of 4.2dl/g.

EXAMPLES 1-2 (Controls) Fibers of Poly(p-phenylene terephthalamide)(PPD-T)

This control example illustrates that the hydrolytic stability ofpoly(p-phenylene terephthalamide) (PPD-T) fiber prepared according tospinning processes described in U.S. Pat. Nos. 3,767,756 (Blades) and4,340,559 (Yang) was improved by heat treatment. A spin solution wasprepared from PPD-T polymer of 6.3 dl/g inherent viscosity at aconcentration of 19.4% by weight PPD-T in 100.1% sulfuric acid and thesolution was extruded through a spinneret at about 80° C. The extrudedfilaments passed through an air gap of 0.25 in (0.64 cm) and thenthrough a coagulating liquid maintained at 2° C. and consisting of waterand 1-5% by weight H₂ SO₄. After washing, neutralizing, and drying onsteam-heated rolls at an inlet tension of about 0.5-0.7 gpd, the dryyarn was wound up at a speed of 250 ypm. The as-spun yarn had a nominal400 denier at 1.5 dpf. It had tensile properties of 23.5 gpd tenacity,3.4% elongation at break, and 706 gpd initial modulus. A sample of thisyarn was tested for hydrolytic stability by immersing it in a 10% byweight NaOH solution at 95° C. for 20 hours. The thus-hydrolyzed yarnwas thoroughly washed with water at room temperature and left to dry atzero tension. The hydrolyzed yarn gave 5.0 gpd retained tenacity, or21.3% retention of its tenacity before hydrolysis.

Under the same conditions as above, except that the fibers were notdried, a never-dried yarn was passed through a tubular oven at 350°-400°C. in 6 sec. The yarn tension at the inlet of the tubular oven wasmaintained at about 1200 g (about 3 gpd). The resulting yarn gavetensile properties of 21.5 gpd tenacity, 2.5% elongation at break, and910 gpd initial modulus. A hydrolytic stability test on the yarn yieldeda retained tenacity of 9.1 gpd, or 42.5% tenacity retention. The yarnproperties are summarized in Table 1 as Example 1.

Under the same spinning and heat treating conditions except that theyarn linear density was reduced, a 214 denier/0.75 dpf heat treated yarnwas prepared. This yarn gave tensile properties of 24.5 gpd tenacity,2.3% elongation at break, and 1091 gpd initial modulus. When hydrolyzedin 10% NaOH solution at 95° C. for 20 hours, it gave a retained tenacityof 15.1 gpd or 61.6% tenacity retention. The yarn properties aresummarized in Table 2 as Example 2 for comparison with other fibers ofsimilar yarn denier and denier per filament.

EXAMPLES 3-17 Fibers of PPD-T/ClT

These examples illustrate further improved hydrolytic stability of heattreated PPD-T/ClT fibers containing 2.5-70 mole % ClT. As shown inTables 1 and 2, the process of Examples 1 and 2 was repeated except thatthe starting polymers were varied. It can be seen that the heat treatedPPD-T/ClT fibers of this invention gave higher retained tenacity andtenacity retention than the PPD-T homopolymer fiber; and that suchfibers with at least 10 mole percent ClT gave much higher retainedtenacity and tenacity retention.

EXAMPLES 18-24 Fibers of PPD-T/ClT/DClT

These examples illustrate similar improvement in the hydrolyticstability of heat treated PPD-T/ClT/DClT fibers over PPD-T homopolymerfiber. The process of Examples 1 and 2, including the heat treatment,was repeated except that copolyamides containing various amounts of ClTand DClT were used, as indicated in Table 3. The heat treatedcopolyamide yarns gave greater values of retained tenacity and %tenacity retention after alkaline hydrolysis in 10% NaOH solution at 95°C. for 20 hours than PPD-T homopolymer fibers prepared under similarspinning and heat treatment conditions.

EXAMPLES 25-32 Fibers of PPD-T and PPD-T/ClT Prepared by High TensionDrying

These examples compare the hydrolytic stability of fibers which wereprepared by high tension drying during fiber preparation according tothe process described in U.S. Pat. No. 4,726,922 (Cochran et al). Theprocesses of Examples 1 and 2 were repeated except that the as-spun yarndrying was conducted at a tension of 2.5 gpd rather than 0.5-0.7 gpd.Upon alkaline hydrolysis in 10% NaOH solution at 95° C. for 20 hours,all of the PPD-T/ClT fibers of at least 10 mole percent ClT gave greatervalues of retained tenacity and % tenacity retention than the PPD-Thomopolymer fibers under the same high tension drying conditions.Results are shown in Table 4.

EXAMPLES 33-34 Fibers Prepared from PPD-T/ClT vs. Blend of PPD-T andPPD-ClT

These examples compare the tensile properties and hydrolytic stabilityof fibers prepared from an 80/20 PPD-T/ClT vs. an 80/20 blend of PPD-Tand PPD-ClT.

In Example 33, the procedure of Example 1 was repeated except that an80/20 PPD-T/ClT copolymer was used as the starting material. Ananisotropic solution of the copolymer in 100.1% H₂ SO₄ at 19.4% polymerconcentration was prepared and extruded at 80° C. to form a continuousfilament yarn through a 0.25 inch air gap and into a coagulation bath ofwater. The spun filaments were washed with water and neutralized withdilute sodium hydroxide solution over rotating rolls. The as-spun yarnwas wound up on a plastic bobbin at 200 ypm. The yarn contained 40filaments at 1.5 dpf. It was kept in a polyethylene bag to prevent itfrom drying. It was later heat treated over a hot shoe at 0° C. under2.5 gpd tension for 6 sec. The tensile properties and hydrolyticstability of these heat treated yarns are summarized in Table 5.

In Example 34, a polymer blend containing 80 wt. % PPD-T and 20 wt. %PPD-ClT was used as the starting material. A continuous filament yarnwas prepared by the same process as was used in Example 33. The as-spunyarn was also kept in a polyethylene bag. It was later heat treatedunder the same conditions as those used in Example 33. The tensileproperties and hydrolytic stability of these heat treated and alkalinehydrolyzed yarns are summarized in Table 5.

EXAMPLE 35 Fibers of Poly(p-phenylene 2-chloroterephthalamide) (PPD-ClT)

This example presents the tensile properties and hydrolytic stability ofheat treated fibers prepared from PPD-ClT homopolymer.

An anisotropic solution was prepared from a PPD-ClT homopolymer asdescribed in Example J at 19.4% polymer concentration in 100.1% H₂ SO₄.The solution was extruded at 80° C. to form a continuous filament yarnin a process similar to that used in Example 1. Alkaline hydrolysis ofthe as-spun yarn resulted in retained tenacity of 9.0 gpd, and tenacityretention of 52.0%. After heat treatment at 300° C. under a tension of 3gpd for 6 seconds in a steam/nitrogen atmosphere, the tenacity was 18.8gpd; and a hydrolytic stability test resulted in a retained tenacity of16.2 gpd, and a tenacity retention of 86.1%.

                                      TABLE 1                                     __________________________________________________________________________    Heat Treated Nominal 400 d/1.5 dpf Yarns                                      Example    1   3   4   5    6   7   8   9 10  35                              Polymer    PPD-T                                                                             PPD-T/ClT                                                      Mole % ClT 0   5   10  20   30  40  50  60                                                                              70  100                             Inh. vis. dl/g                                                                           6.3 7.7 7.6 5.9  5.9 5.4 4.7 5.2                                                                             3.9 4.2                             __________________________________________________________________________    AS SPUN YARN                                                                  Denier     403 379 354 400  356 344 328       420                             Dpf        1.5 1.42                                                                              1.33                                                                              1.5  1.33                                                                              1.29                                                                              1.23      1.5                             Tenacity, gpd                                                                            23.5                                                                              25.7                                                                              25.9                                                                              25.0 18.4                                                                              16.1                                                                              20.6      17.2                            Elongation, %                                                                            3.4 3.1 3.1 3.5  2.8 2.6 3.5       4.5                             Modulus, gpd                                                                             706 800 855 720  684 686 650       601                             Moisture regain, %                                                                       4.2 4.0 3.7 3.6  3.5 2.9 2.5 1.9                                   Hydrolytic Stability                                                          Retained tenacity, gpd                                                                   5.0 6.6 9.0 11.5 10.7                                                                              11.4                                                                              13.4      9.0                             Tenacity retention, %                                                                    21.3                                                                              25.7                                                                              34.7                                                                              46.0 58.2                                                                              70.8                                                                              65.0      52.0                            HEAT TREATED YARN                                                             Tenacity, gpd                                                                            21.5                                                                              28.0                                                                              26.5                                                                              21.3               22.9                                                                              18.8                            Elongation, %                                                                            2.5 3.3 2.8 2.2                3.0 2.5                             Modulus, gpd                                                                             910 838 977 1037               870 849                             Hydrolytic Stability                                                          Retained tenacity, gpd                                                                   9.1 9.8 13.9                                                                              15.6               20.7                                                                              16.2                            Tenacity retention, %                                                                    42.5                                                                              35.0                                                                              52.5                                                                              58.9               90.4                                                                              86.1                            __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Heat Treated 200-300 d/1-0.75 dpf Yarns                                       Example    2    11  12  13  14  15  16  17                                    Polymer    PPD-T                                                                              PPD-T/ClT                                                     Mole % ClT 0    5   10  20  30  40  50  60                                    Inh. vis. dl/g                                                                           6.3  7.7 7.6 5.9 5.9 5.4 4.7 5.2                                   __________________________________________________________________________    AS SPUN YARN                                                                  Denier                  231     205 225                                       Dpf                     0.87    0.77                                                                              0.84                                      Tenacity, gpd           23.1    20.6                                                                              20.4                                      Elongation, %           3.1     2.8 2.4                                       Modulus, gpd            746     791 714                                       Hydrolytic Stability                                                          Retained tenacity, gpd  13.5    13.7                                                                              15.3                                      Tenacity retention, %   58.4    66.5                                                                              75.0                                      HEAT TREATED YARN                                                             Tenacity, gpd                                                                            24.5 28.6                                                                              26.7                                                                              22.0                                                                              21.3                                                                              20.3                                                                              18.6                                                                              21.1                                  Elongation, %                                                                            2.3  3.1 2.8 2.3 2.3 2.7 2.1 3.1                                   Modulus, gpd                                                                             1091 931 912 934 952 779 934 827                                   Hydrolytic Stability                                                          Retained tenacity, gpd                                                                   15.1 15.8                                                                              15.3                                                                              19.9                                                                              15.8                                                                              16.6                                                                              18.0                                                                              16.9                                  Tenacity retention                                                                       61.6 55.2                                                                              57.3                                                                              90.5                                                                              74.2                                                                              81.8                                                                              96.8                                                                              80.1                                  __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Heat Treated PPD-T/ClT/DClT Yarns                                             Example    18  19  20  21   22  23  24                                        Polymer    PPD-T/ClT/DClT                                                     Mole % ClT/DClT                                                                          16/4.5  8/3      0/5 0/10                                                                              0/18                                      Inh. vis. dl/g              6.2 5.6 4.8                                       __________________________________________________________________________    HEAT TREATED YARN                                                             Yarn denier                                                                              187 398 385 193  418 410 514                                       Average dpf                                                                              0.7 1.5 1.5 0.7  1.5 1.5 1.9                                       Tenacity, gpd                                                                            20.4                                                                              19.0                                                                              24.3                                                                              20.6 23.8                                                                              23.0                                                                              22.3                                      Elongation, %                                                                            2.4 2.1 2.8 2.4  2.8 3.3 3.2                                       Modulus, gpd                                                                             875 915 863 1001 879 733 771                                       Hydrolytic Stability                                                          Retained tenacity, gpd                                                                   18.1                                                                              16.8                                                                              11.8                                                                              19.1 13.5                                                                              10.6                                                                              14.9                                      % Tenacity retention                                                                     88.7                                                                              88.4                                                                              48.6                                                                              92.7 56.7                                                                              46.1                                                                              66.8                                      __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    High Tension Dried Yarns                                                      Example    25  26   27  28  29  30  31  32                                    Polymer    PPD-T    PPD-T/TCl                                                 Mole % ClT 0        10  20  40  50  60  70                                    Inh. vis. dl/g                                                                           6.3 6.3  7.6 5.9 5.9 4.7 5.2 3.9                                   __________________________________________________________________________    AS SPUN YARN                                                                  Yarn denier                                                                              386 214  370 234 334 321 234 370                                   Dpf        1.45                                                                              0.80 1.4 0.88                                                                              1.25        1.39                                  Tenacity, gpd                                                                            24.5                                                                              23.3 26.5                                                                              23.4                                                                              23.0                                                                              20.6                                                                              19.5                                                                              19.8                                  Elongation, %                                                                            2.5 2.3  2.8 3.1 2.9 2.5 2.4 3.8                                   Modulus, gpd                                                                             989 1035 977 789 854 891 868 664                                   Hydrolytic Stability                                                          Retained tenacity, gpd                                                                   10.5                                                                              11.6 13.1                                                                              16.0                                                                              16.0                                                                              18.1                                                                              16.6                                                                              17.0                                  % Tenacity retention                                                                     42.9                                                                              49.8 49.4                                                                              68.3                                                                              89.6                                                                              87.9                                                                              85.1                                                                              85.9                                  __________________________________________________________________________

                  TABLE 5                                                         ______________________________________                                        Fibers of PPD-T/ClT vs. Blend of PPD-T and PPD-ClT                                          Example                                                                       33     34         1                                                           Polymer                                                                         80/20    80/20 blend                                                                              Homo-                                                     PPD-T/   of PPD-T   polymer                                   HEAT TREATED YARN                                                                             ClT      and PPD-ClT                                                                              PPD-T                                     ______________________________________                                        Denier          63.8     61.6       403                                       Tenacity, gpd   24.5     24.2       21.5                                      Elongation, %   3.0      3.2        2.5                                       Modulus, gpd    847      719        910                                       Hydrolytic Stability                                                          Retained tenacity, gpd                                                                        14.2     13.7       9.1                                       Tenacity retention, %                                                                         58.0     56.6       42.5                                      ______________________________________                                    

I claim:
 1. An aromatic polyamide yarn of an aromatic polyamide from (1)at least one aromatic diamine and (2) at least one aromatic diacidchloride wherein (2) comprises at least 10 mole percentchloroterephthaloyl chlorides;the yarn exhibiting a tenacity of greaterthan 18 grams per denier and a hydrolytic stability of greater than 60%.2. The yarn of claim 1 wherein (2) comprises at least 20 mole percentchloroterephthaloyl chlorides.
 3. The yarn of claim 1 wherein thechloroterephthaloyl chlorides are more than 70 mole percentmonochloroterephthaloyl chloride.
 4. The yarn of claim 1 wherein thechloroterephthaloyl chlorides are more than 70 mole percentdichloroterephthaloyl chloride.
 5. The yarn of claim 1 wherein thechloroterephthaloyl is present in a copolymer of diamine and acombination of terephthaloyl chloride and chloroterephthaloyl chloride.6. An aromatic polyamide yarn of a blend of aromatic polyamidehomopolymers from (1) an aromatic diamine and (2) an aromatic diacidchloride selected from the group consisting of terephthaloyl chlorideand chloroterephthaloyl chlorides and wherein the chloroterephthaloyl ispresent in one homopolymer of the blend of homopolymers.
 7. The yarn ofclaim 1 wherein the aromatic polyamide is copoly(p-phenyleneterephthalamide/chloroterephthalamide).
 8. The yarn of claim 1 whereinthe aromatic polyamide is copoly(p-phenyleneterephthalamide/dichloroterephthalamide).
 9. The yarn of claim 1 whereinthe aromatic polyamide is copoly(p-phenyleneterephthalamide/chloroterephthalamide)/dichloroterephthalamide).
 10. Theyarn of claim 1 wherein the aromatic polyamide is poly(p-phenyleneterephthalamide) and poly(p-phenylene chloroterephthalamide).
 11. Theyarn of claim 1 wherein the tenacity is greater than 20 grams per denierand the hydrolytic stability is greater than 70%.
 12. The yarn of claim11 wherein at least 20 mole percent of the aromatic diacid chlorides arechloroterephthaloyl chlorides.
 13. A copoly(p-phenyleneterephthalamide/chloroterephthalamide) yarn of a copoly(p-phenyleneterephthalamide/chloroterephthalamide) from (1) p-phenylene diamine and(2) at least one diacid chloride selected from terephthaloyl chlorideand chloroterephthaloyl chloride wherein (2) comprises at least 10 molepercent of chloroterephthaloyl chlorides;the hydrolytic stability andtenacity of the yarn being greater than the hydrolytic stability and thetenacity of a yarn of the same dimensions and made by the sameprocesses, but using a homopolymer of poly(p-phenylene terephthalamide).